Fuel pump with carbs, Should it run all the time? Options

[mlindner]

Thanks all. Porschetub, I ordered the one you recommended. Do you have a picture where you mounted yours?

Mounting of the regulator or the pump ?.
My pump is mounted to my alloy suspension cross member and protected by the under tray , my regulator is mounted to the rear engine bulkhead up high so I can read the gauge .
I researched this setup and found it was the most common used ,IMO the best way to go ,cheers ,sorry can't find any pics ,it was a long time ago.

yes, my picture is of the filter and pump up front, fuel regulator is on engine rear bulk head. Best

[mlindner]

Also where should the gauge be located? The FPR has one line in and 2 out to the carbs, will it matter where it’s located after the FPR?
Thanks again guys!

In the engine compartment, rear bulk head, easy shot to the carbs.

[brooks944]

Thanks, does the gauge placement matter after the FPR, either side or where it’s easier to see?

[porschetub]

Thanks all for responses. Does anyone have pictures of where they located the regulator? I got the Holley one that was recommended with the gauge, and now request your input on where to locate. porschetub had his on the rear engine bulkhead, anyone else have their’s there and some pics or other recommended locations?
Again, thanks for everyone’s help.
Rick

I have a six conversion so mounting there was best for me considering carb layout and ability to read the gauge easily , but you will need a "tee fitting" downstream from the regulator then you can mount your gauge there and read it easily .
Use FI fuel hose clamps not the screw thread type as they chew up the hose ,best hose is Gates Barricade hands done ,tried other brands not ethanol rated as advertised !!!.
Good luck ,cheers.

[VaccaRabite]

Most by the steering rack or under the tank. I put mine more up front for easy access under a modified fuel tank. Should be in the push position. Best, mark

I did the same thing with an off cut of copper nickel line! Except mine is under the fuel tank.

I got tired of the under tank lines kinking. That 180 degree bend from the pump to the tunnel was always kinking. Fixed it easy peasy by making a hardline for that bend.

Zach

[brooks944]

Got the recommended regulator and gauge installed, thanks for all the help, fuel pressure is below 3. Went for a drive today and the car is backfiring under load. It sounds like the backfire is coming from the carb directly behind the driver, but I can’t be sure. Idles fine and can rev with no issues. What should I check into next? Thanks!

[technicalninja]

pull main and idle jets, clean the piss out of them. Make sure the idle jets have good O-ring (bad about leaking air into idle fuel stream).

I use HBNR AC O-rings all the time, but I run an automotive AC shop...

Blown out jet ports with low pressure air (50psi).

Hold jets in front of light, you can see stuck crap this way.

Clean it all up good, re-assemble, verify secondary ignition is good (plugs wires, distributer cap/rotor. Looks for "carbon tracts" in cap/rotor.

Verify strong blue spark to each plug.

Go drive, popping still happening?

Compression test first and then leak down test.

Eliminate spark and fuel as the issue and it will come down to intake valve on the back firing cylinder will have poor seat contact.
Valve adjustment might fix it if too tight.

My 1st 914 was afflicted with this. It didn't backfire all the time but sometimes it would shoot flames from the center mount progressive carb badly.

One night, leaving a young ladies house at 3am, trying not to wake her parents, I set their tree on fire with that damn 914...

[brant]

Please install any pressure guage onto a chassis point and not onto any engine mounting point.

the engine rocks... vibrates... moves around.

I've seen brass fuel line fittings work harden and crack when mounted onto the motor instead of the chassis.

helped put out a 911 engine fire at the track due to exactly this... cracked T fitting...

you don't want to mount to the motor assembly or anything supported by motor mounts....

[Jack Standz]

Got the recommended regulator and gauge installed, thanks for all the help, fuel pressure is below 3. Went for a drive today and the car is backfiring under load. It sounds like the backfire is coming from the carb directly behind the driver, but I can’t be sure. Idles fine and can rev with no issues. What should I check into next? Thanks!

Backfires can be caused by several things. It means the mixture is igniting where/when you don't want it. This is not good. This can damage your motor.

Too lean or too rich mixture. Generally, a backfire through the carb is a lean mixture, a backfire through the exhaust is too rich.

Ignition timing is off.

Valve(s) is/are leaking.

Best wishes for a successful fix!

[Jack Standz]

Mixture: An Air Fuel Ratio meter/gauge is a very good tool for getting your mixture right (make sure you have the right: main jets, idle jets, pump jets, venturis, emulsion tubes, etc.).

Ignition timing: A very good tool for getting your ignition timing right is a "dial back" timing light. But, be sure to put a mark on your fan/flywheel at TDC on compression for #1 cylinder. Give the motor what it wants, but a good starting point would be maybe around 8 degrees Before Top Dead Center (BTDC) at idle with maybe 28 to 32 degrees total advance. Again, give your motor what it wants.

Valves: You can use a vacuum gauge for a preliminary check, but use a leak down test.

If this is more than you know how to do at this point, no problem. Find someone that can do these types of test and troubleshooting.

[rhodyguy]

For my carb pump, I removed the pump wire plug (don’t throw it away) for the stock pump and made up a wire extension to provide power. Don’t power the pump off of the distributor.